Constructing a swept solid
Let me unpack this one by one :)

1. Fill caps
You need to check Fill Caps in Geometry > Bevel > Fill Caps  



2. Overlapping geometry
This is a result of beveling multiple curves into one point.
You'll have to manually clean it up, or use the Boolean modifier, etc.

3. Too many faces
To adjust the amount of faces change the values in Shape > Preview/render resolution.
You can do this for both of your curve shapes.



Here is the edited .blendfile